“People thought that PCB issues were solved and they could forget about it," Rodenburg told Yahoo Shine. "But now we are finding new sources in the environment."

The work has undergone peer review, and she hopes the team's findings will be published later this year.

PCBs have been extensively studied, and while PCB 11 was considered safe because the body metabolizes and excretes the chemical more quickly than other PCBs, Rodenburg said little is actually known about PCB 11 and its toxicity levels in humans.

“It’s out there in levels that are worrisome,” Rodenburg told SA. It is an unintentional byproduct of manufacturing pigment.

An Environmental Protection Agency spokesperson told SA that although PCBs are banned, federal regulations “recognize that some products (e.g., pigments and dyes) contain inadvertently generated PCBs.” The risk of PCB 11 is being reviewed by the EPA.

“Everyone has ignored the lower chlorinated congeners, primarily because they are not persistent and are relatively easily metabolized in the human body,” Dr. David Carpenter, director of the Institute for Health and the Environment at the University at Albany-SUNY, told SA.

University of Iowa researchers last year found PCB 11 could interfere with cell signaling.